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Does antimatter fall down or up?

Antimatter

The observable universe is composed almost entirely of matter but we can
produce stuff called antimatter in the lab. Antimatter is material composed of
antiparticles.

Antiparticles have the same mass as normal matter particles but the opposite
charge. When an antiparticle collides with an ordinary matter particle they
both annihilate - producing a burst of other particles and radiation.

Antiparticles should interact gravitationally just like particles of ordinary
matter because Einstein's weak equivalence principle states that gravity
doesn't depend on composition. But if they don't then gravity is much more
complicated than our current understanding indicates.

The experiment

The AEgIS experiment at CERN shoots antihydrogen atoms horizontally -
whereupon they fly and fall - at a wall made of matter. On hitting the wall
the antihydrogen annihilates with a matter nucleus in the wall to produce a
burst of mostly pions and some heavier particles. These particles travel
through a special gel called an emulsion which makes their tracks visible.
Pions leave thin tracks while heavier particles leave much fatter tracks.

Tracing these tracks to their point of origin tells the AEgIS team exactly
where the annihilation occurred, which in turn allows them to calculate how
far each particle travels. They can then work out - from the distance each
particle flew and fell - how antimatter interacts with gravity.

AEgIS will start annihilating antihydrogen atoms in 2015. In the meantime the
team needs to better understand the process of annihilation by shooting
antiprotons at different target materials which will result in different kinds
of particle bursts. AEgIS scientists need to fine-tune their understanding of
annihilation by mapping the particle tracks and counting the number of thin
and fat tracks for many particle bursts.

AEgIS experiment installation

Particle tracks in the emulsion

Your mission

Humans are way better at interpreting the particle tracks than machines so the
AEgIS team needs your big brains and keen eyes to map the particles’ path
through the emulsion. All you have to do is join the dots!

AEgIS scientists also want to be able to classify each track as fat or thin.
Please get in touch if you would like to help to write the software to carry
out this classification.

The images here have been uploaded directly from AEgIS and have not yet been
analyzed by scientists. In fact, this is the first time CERN has released
detector data for public analysis. So you can be the first to analyze this
data and make a real contribution to CERN’s research.

The input you provide will be openly available and the results will be
visualized on this page as a 3D Model.